Digital Subscriber Line (DSL) networks, such as G.SHDSL, allow flexible, high-speed data transmission rates over standard copper interfaces. Normally a single line unit at a central office location is connected to a single remote unit using one or two G.SHDSL pairs for increased bandwidth. A very useful enhancement to this standard configuration is point-to-multipoint, where a single line unit at a central office is connected to two remote units, using a single G.SHDSL pair to each remote unit. A point-to-multipoint network implementation provides cost advantages over point to point because it eliminates the need to install separate DSL line units at a central office for each remote unit served by the central office. Further, point-to-multipoint allows service providers to offer fractional G.703/E1 lines to customers who may not require the entire bandwidth capacity provided by a full G.703/E1 line.
One useful feature of a full G.703/E1 interface line is the Channel Associated Signaling (CAS) signaling bits carried in timeslot 16 of each E frame. CAS signaling bits use routing information to direct voice/data payloads carried by a G.703/E1 interface line to its destination. Because G.703/E1 signal channels are dedicated to single interface applications, one problem with point-to-multipoint applications in the art today is that there is no means for communicating CAS signaling bits between a central office line unit and the line units of one or more remote units having fractional G.703/E1 lines that share the central office line unit's single G.703/E1 interface.
For the reasons stated above and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for improved systems and methods for point-to-multipoint data communications with CAS signaling.